דבר שלא בא לעולם חלק א - רקע בדיני קניין

How so? If the buyer took the produce from the seller, but the buyer did not yet give the seller the money, he cannot renege on the transaction.

If the buyer gave the seller money, but did not yet take the produce from him, he can renege on the transaction. However, they said: He Who exacted payment from the people of the generation of the flood, and from the generation of the dispersion, will in the future exact payment from whoever does not stand by his statement.

Rabbi Shimon says: Whoever has the money in their hands is at an advantage.

Rabbi Zeira said: A person should not transfer ownership of the four species to a child on the first day of the Festival. What is the rationale? A child is capable of acquiring objects, but not of giving them away. And in that case, a situation will result where the adult is seeking to fulfill his obligation with a lulav that is not his.

And Rabbi Zeira said: A person should not say to a child: I will give you something, and then not give it to him, because he is teaching his child to lie. As it says, “They have taught their tongues to speak lies” (Jeremiah 9:4).

"But not of giving them away." He cannot give it back to this father as a gift, because he is not a "Bar Da'at"